Two concomitant polymorphs of 3,3′,4,4′-tetrakis(phenylethynyl)-1,1′-[2,2,2,-trifluoro- 1-(trifluromethyl)ethanediyl]bisbenzene |
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| Authors: | K Prasanna U Perera Khalil A Abboud Mariusz Krawiec Don VanDerveer Dennis W Smith Jr |
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| Institution: | (1) Department of Chemistry, Clemson University, Clemson, South Carolina, U.S.A.;(2) Department of Chemistry, University of Florida, Gainesville, Florida, U.S.A. |
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| Abstract: | A representative compound of bis-ortho-diynyl arene (BODA), with a general formula (m,p)R2–Ph]2
–X, where R: –C≡C–Ph and X: >C(CF3)2 has been structurally characterized. The compound is being investigated as a monomer for high-performance polyarylene networks and glassy carbon precursors. The bis(trifluoromethyl) derivative crystallizes in two concomitant polymorphic forms. The two polymorphs form a monotropic system with melting points of 436 and 463 K. The metastable form yields monoclinic crystals (P21/n, Z=4). a=12.677(3) ?, b=11.677(2) ?, c=24.026(5) ?, β=93.79(3)°. The thermodynamically stable form is monoclinic as well (P21/c, Z=8), a=10.7983(6) ?, b=30.628(2) ?, c=21.648(1) ?, β=94.737(1)° with small voids indicating less efficient packing. The two polymorphs contain different conformers of the rotationally flexible molecule. |
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| Keywords: | Polyarylenes polymorphism BODA enediynes Bergman cyclization |
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